Commit b3bd0249 authored by Sven Schnelle's avatar Sven Schnelle Committed by Vasily Gorbik
Browse files

s390/stp: add locking to sysfs functions 



The sysfs function might race with stp_work_fn. To prevent that,
add the required locking. Another issue is that the sysfs functions
are checking the stp_online flag, but this flag just holds the user
setting whether STP is enabled. Add a flag to clock_sync_flag whether
stp_info holds valid data and use that instead.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Reviewed-by: default avatarAlexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent fa6999e3

arch/s390/kernel/time.c

+85 −33
Original line number Diff line number Diff line
@@ -301,6 +301,7 @@ static unsigned long clock_sync_flags; 


#define CLOCK_SYNC_HAS_STP		0

#define CLOCK_SYNC_STP			1

#define CLOCK_SYNC_STPINFO_VALID	2



/*

 * The get_clock function for the physical clock. It will get the current
@@ -535,6 +536,22 @@ void stp_queue_work(void) 
	queue_work(time_sync_wq, &stp_work);

}



static int __store_stpinfo(void)

{

	int rc = chsc_sstpi(stp_page, &stp_info, sizeof(struct stp_sstpi));



	if (rc)

		clear_bit(CLOCK_SYNC_STPINFO_VALID, &clock_sync_flags);

	else

		set_bit(CLOCK_SYNC_STPINFO_VALID, &clock_sync_flags);

	return rc;

}



static int stpinfo_valid(void)

{

	return stp_online && test_bit(CLOCK_SYNC_STPINFO_VALID, &clock_sync_flags);

}



static int stp_sync_clock(void *data)

{

	struct clock_sync_data *sync = data;
@@ -557,8 +574,7 @@ static int stp_sync_clock(void *data) 
			if (rc == 0) {

				sync->clock_delta = clock_delta;

				clock_sync_global(clock_delta);

				rc = chsc_sstpi(stp_page, &stp_info,

						sizeof(struct stp_sstpi));

				rc = __store_stpinfo();

				if (rc == 0 && stp_info.tmd != 2)

					rc = -EAGAIN;

			}
@@ -604,7 +620,7 @@ static void stp_work_fn(struct work_struct *work) 
	if (rc)

		goto out_unlock;



	rc = chsc_sstpi(stp_page, &stp_info, sizeof(struct stp_sstpi));

	rc = __store_stpinfo();

	if (rc || stp_info.c == 0)

		goto out_unlock;
@@ -641,10 +657,14 @@ static ssize_t ctn_id_show(struct device *dev, 
				struct device_attribute *attr,

				char *buf)

{

	if (!stp_online)

		return -ENODATA;

	return sprintf(buf, "%016llx\n",

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid())

		ret = sprintf(buf, "%016llx\n",

			      *(unsigned long long *) stp_info.ctnid);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(ctn_id);
@@ -653,9 +673,13 @@ static ssize_t ctn_type_show(struct device *dev, 
				struct device_attribute *attr,

				char *buf)

{

	if (!stp_online)

		return -ENODATA;

	return sprintf(buf, "%i\n", stp_info.ctn);

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid())

		ret = sprintf(buf, "%i\n", stp_info.ctn);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(ctn_type);
@@ -664,9 +688,13 @@ static ssize_t dst_offset_show(struct device *dev, 
				   struct device_attribute *attr,

				   char *buf)

{

	if (!stp_online || !(stp_info.vbits & 0x2000))

		return -ENODATA;

	return sprintf(buf, "%i\n", (int)(s16) stp_info.dsto);

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid() && (stp_info.vbits & 0x2000))

		ret = sprintf(buf, "%i\n", (int)(s16) stp_info.dsto);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(dst_offset);
@@ -675,9 +703,13 @@ static ssize_t leap_seconds_show(struct device *dev, 
					struct device_attribute *attr,

					char *buf)

{

	if (!stp_online || !(stp_info.vbits & 0x8000))

		return -ENODATA;

	return sprintf(buf, "%i\n", (int)(s16) stp_info.leaps);

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid() && (stp_info.vbits & 0x8000))

		ret = sprintf(buf, "%i\n", (int)(s16) stp_info.leaps);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(leap_seconds);
@@ -686,9 +718,13 @@ static ssize_t stratum_show(struct device *dev, 
				struct device_attribute *attr,

				char *buf)

{

	if (!stp_online)

		return -ENODATA;

	return sprintf(buf, "%i\n", (int)(s16) stp_info.stratum);

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid())

		ret = sprintf(buf, "%i\n", (int)(s16) stp_info.stratum);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(stratum);
@@ -697,9 +733,13 @@ static ssize_t time_offset_show(struct device *dev, 
				struct device_attribute *attr,

				char *buf)

{

	if (!stp_online || !(stp_info.vbits & 0x0800))

		return -ENODATA;

	return sprintf(buf, "%i\n", (int) stp_info.tto);

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid() && (stp_info.vbits & 0x0800))

		ret = sprintf(buf, "%i\n", (int) stp_info.tto);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(time_offset);
@@ -708,9 +748,13 @@ static ssize_t time_zone_offset_show(struct device *dev, 
				struct device_attribute *attr,

				char *buf)

{

	if (!stp_online || !(stp_info.vbits & 0x4000))

		return -ENODATA;

	return sprintf(buf, "%i\n", (int)(s16) stp_info.tzo);

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid() && (stp_info.vbits & 0x4000))

		ret = sprintf(buf, "%i\n", (int)(s16) stp_info.tzo);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(time_zone_offset);
@@ -719,9 +763,13 @@ static ssize_t timing_mode_show(struct device *dev, 
				struct device_attribute *attr,

				char *buf)

{

	if (!stp_online)

		return -ENODATA;

	return sprintf(buf, "%i\n", stp_info.tmd);

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid())

		ret = sprintf(buf, "%i\n", stp_info.tmd);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(timing_mode);
@@ -730,9 +778,13 @@ static ssize_t timing_state_show(struct device *dev, 
				struct device_attribute *attr,

				char *buf)

{

	if (!stp_online)

		return -ENODATA;

	return sprintf(buf, "%i\n", stp_info.tst);

	ssize_t ret = -ENODATA;



	mutex_lock(&stp_work_mutex);

	if (stpinfo_valid())

		ret = sprintf(buf, "%i\n", stp_info.tst);

	mutex_unlock(&stp_work_mutex);

	return ret;

}



static DEVICE_ATTR_RO(timing_state);